JavaScript RegExp Flags

RegExp Modifier Flags

Flags are parameters that can modify how a regex pattern is used, such as making it case-insensitive or global.

JavaScript Regex Flags

Revised July 2025

Flag

Description

Performs case-insensitive matching

Performs multiline matching

An upgrade to the /u flag for better Unicode support (new 2025)

Flag Syntax: /pattern/flags

Opening delimiter for the regular expression pattern

Closing delimiter for the regular expression flags

One or more single modifier flags

RegExp /g Flag (Global)

The

Example

A global search for "is" in a string:
let text = "Is this all there is?";
const pattern = /is/g;
let result = text.match(pattern);

RegExp /i Flag (Insensitive)

The

/i flag makes the match case - insensitive: /abc/i matches "abc", "AbC", "ABC".

Example

A case - insensitive search for "w3schools" in a string:

let text = "Visit W3Schools";
const pattern = /is/g;
let result = text.match(pattern);

RegExp /d Flag

The

Example

let text = "aaaabb";
const pattern = /(aa)(bb)/d;
let result = text.match(pattern);

RegExp /s Flag (Single line/DotAll)

The

Example

Without the /s flag, \n does not match . (wildchars):

let text = "Line\nLine.";
const pattern = /Line./gs;
let result = text.match(pattern);

RegExp /y Flag (Sticky):

The

The

Examples let text = "abc def ghi";
const pattern = /\w+/y;
// Start match from position 4 pattern.lastIndex = 4;
let result = text.match(pattern);

The /y flag must be set to allow match from a position.

This will not work:

let text = "abc def ghi";
const pattern = /\w+/;
// Start match from position 4 pattern.lastIndex = 4;
let result = text.match(pattern);

The example above uses a regex metacharacter

The meaning of

RegExp /u Flag (Unicode)